1. Field of the Invention
The present invention relates to a shearing machine, and more particularly to shearing machine wherein a sheared portion of a plate workpiece is supported at the rear of a shearing region in which the workpiece is sheared by means of a lower blade and an upper blade provided on a ram with free vertical movement, and wherein a conveyor means for conveying the separated plate sheared from the workpiece in the rear direction is provided so that it swings freely in the vertical direction and moves freely in the backward and forward direction.
2. Description of the Related Art
In commonly known shearing machines, a long lower blade extending in the lateral direction is mounted on the rear section of a work table, and an upper blade which shears a plate workpiece in cooperation with this lower blade is mounted on the lower part of a ram with free vertical movement, angled to the horizontal. In order to support the portion of the workpiece which protrudes from the work table in the rear direction When the workpiece is sheared by the action of the upper and lower blades in cooperation, and to convey this portion in the rear direction after shearing, a conveying means, such as, for example, a conveyor belt, is positioned at the rear of the shearing region from the upper and lower blades.
In a configuration as outlined above, when the ram descends to shear the workpiece, there is mutual interference between the ram and the conveying means so that it is necessary to lower the conveying means to eliminate this interference.
Accordingly, as a conventional configuration, a means, such as, for example, an air cylinder or the like, is provided to move the conveying means vertically. In this configuration, in order to eliminate the interference between the conveyor means and the ram it is necessary to first lower the conveying means and then lower the ram. Accordingly, when the ram first descends, the conveying means is already in the state where support has been removed from the workpiece. The portion of the workpiece which projects to the rear from the work table is therefore capable of bending from its own weight. Accordingly, in this configuration the effective support of the workpiece deteriorates and it is difficult to further improve the shearing precision. Also, in the configuration where the conveying means is moved vertically by means of an air cylinder or the like, because of the characteristics of the air cylinder or the like, the repeatability is limited from the velocity of the vertical movement of the conveyor means and improvement of productivity is hindered.
In addition, as an another conventional configuration, the ram and the conveying means are connected in a mutually pivotable manner through a link or the like. In this configuration the conveying means moves vertically integrated with the vertical motion of the ram, and, as a result, high speed shearing becomes possible and it is therefore possible to further improve the productivity. However, because this conveying means descends simultaneously with the start of the descent of the ram, the removal of the support of the workpiece also occurs simultaneously with the start of the descent of the ram, and the effective support of the workpiece deteriorates in the same manner as the previously discussed configuration.
Also, as is commonly known, in a shearing machine, when the workpiece is sheared by means of the upper and lower blades a plate restraint means is provided to secure the workpiece to the work table by pressure.
Conventionally, an air cylinder or a hydraulic cylinder is utilized as the plate restraint means. An advantage of a configuration of this type is the ease with which the pressure used in securing the workpiece can be adjusted. However, a diverter valve is required in the fluid pressure circuit and in the case of a high velocity shear in which the shearing is repeated at high velocity there is the problem that it becomes difficult to follow up the high velocity repetition.
Accordingly, in a high velocity shear a spring is used as the plate restraint means which secures the workpiece to the work table. In this mechanism, a pressure member which presses the workpiece is always energized in the downward direction by means of this spring, and when the ram begins to descend, the pressure member almost simultaneously secures the workpiece to the work table.
From this configuration there is good follow-up ability in the pressure member to follow-up the elevating action of the ram. However, there is a problem that the energizing force which presses the pressure member in the downward direction is not adjustable; and, in the case of a soft workpiece the workpiece will be compressed by the pressure member.
In addition, in a shearing machine in which the conveying means is positioned to the rear of the shearing region from the upper blade and the lower blade, a usual configuration is to position at the rear of the conveying means a storage means for storing the separated plate conveyed by the conveying means. In this type of configuration, a rear stopper is mounted on the rear side of the storage means to align the rear sides of the separated plates which are dropped from the conveying means, and a guide means is provided on the front side of the storage means to guide the separated plates dropped from the conveying means and align the front sides of the separated plates.
However, in the configuration in which the conveying means is provided at the rear of the shearing region so as to be movable to the backward, the guide means is provided at a position lower than the conveying means to eliminate interference between the conveying means and the guide means. Accordingly, the problem arises that a difference of the elevation between the storage means and the storage means where the separated plates is dropped from the conveying means to be stored, become large, and the the inclination of the separated plates while being dropped becomes great; this results in that the angled section or the side section of the separated plate hits the upper surface of the separated plates which are already accumulated, causing deformation or abrasion damage or the like being easily produced on the upper surface of the separated plate.